The present invention relates to a method and apparatus for detecting defects in a pattern having directionality as a pattern formed on a semiconductor pellet, for example.
The manufacturing process of semiconductor devices includes several steps of: for example, forming a plurality of semiconductor regions by injecting impurities into a semiconductor wafer, forming an oxide film and an electrode layer on the semiconductor wafer, dividing the semiconductor wafer into a plurality of chips, and applying the wire bonding to the separated chips. As is well known, the manufacturing process of a semiconductor device is a typical example of the fine work requiring complicated and sophisticated technique to manufacture. When a defect is found in the pattern during the course of the manufacturing process, it is desirable, therefore, to pick up and remove such defective semiproduct before the process reaches the final step.
Many approaches to inspect defects in a pattern formed on the semiconductor wafer surface have been proposed. In one of such proposals the configurations of the corresponding portions in the two adjacent chips on a semiconductor wafer are successively compared. When an inconsistency is found in the results of the successive comparisons, it is determined to be a defect. Before the wafer is divided into a number of individual chips, this approach can secure a highly accurate detection because the relative positions of the chips are fixed, and the corresponding portions to be compared can easily and correctly be specified. It is evident, however, that defect detection cannot be carried out in the steps following the wafer dividing step, for example, in the dicing step for obtaining individual chips and the step for picking up these individual chips. For this reason, the approach under discussion requires another defect detection step after chip separation. The additional defect detection step, however, encounters a difficulty in specifying the corresponding portions on the adjacent chips to be compared, since those individual chips are separated. This difficulty in specifying the corresponding portions on the chips leads to inaccurances in the detection.